Ozone is known to have a strong oxidizing power and therefore has found extensive applications in various fields, e.g., sterilization, removal of odors, preservation of the freshness and the like. In particular, such a method is employed for disinfection of aqueous solutions, where an ozone-containing water prepared by placing ozone in gas bubbles contained in an aqueous solution is used.
For example, Japanese Patent Unexamined Publication (JP Kokai) 2004-60010 proposes an apparatus for efficiently dissolving ozone in an aqueous solution, that is, an apparatus for producing ozone-containing water where ozone is steadily dissolved in the aqueous solution.
The ozone-containing water as mentioned above shows high ozone contents when just produced. However, when the ozone-containing water is kept under normal temperature and pressure, ozone dissolved in the aqueous solution will mostly dissipate out in approximately one or two hours after the production of the ozone-containing water, for example, by diffusion from the surface of the aqueous solution. This means considerable decrease in the sterilizing effect. There has been the problem that long-term storage of the ozone-containing water is impossible.